Tapping its network of nearby on-duty private livery cars, UberCab is an iPhone app that enables you to hail a Town Car online and have a driver confirm that it will pick you up at your GPS-determined location.

The battle is on for two transportation network start-ups that are poised to go head-to-head at SXSW to promote a very similar business model: using an app to book a ride from a network of private cars.

Uber, a mobile limousine-booking service, has become a favorite among in-the-know techies in San Francisco. Launching its service in New York, where taxis are heavily regulated and easy to find already, may prove more complicated.

Uber (formerly UberCab), which received a cease-and-desist order from the San Francisco Municipal Transportation Authority, is alive and kicking despite the SF taxi commission's best attempt at squelching the private car network. In fact, the company is looking to expand in 2011.